$sort:

In MongoDB, the $sort operator is used in the MongoDB Shell (mongoshell) as part of the Aggregation Framework to sort the documents in an aggregation pipeline based on specified criteria.


The $sort operator allows you to reorder the documents in the pipeline output based on one or more fields.

 You can sort the documents in either ascending (default) or descending order.


The basic syntax of the $sort operator in the MongoDB Shell is as follows:

{
  $sort: 
{
    field1: <sort order>,
    field2: <sort order>,
    ...
  }
 }

Let's explore the main components of the $sort operator:


$sort: This is the stage of the aggregation pipeline where you define the sorting operation.


$sort key ordering must be 1 (for ascending) or -1 (for descending)

field1<1 or -1>, field2, etc.: These represent the fields by which you want to sort the documents. 

You can specify one or more fields for sorting. 

If multiple fields are provided, MongoDB applies the sort order sequentially based on the order of the fields specified.


<sort order>: This specifies the sort order for each field. 

The sort order can be either 1 for ascending order (default) or -1 for descending order.


Here's an example to illustrate the usage of the $sort operator in the MongoDB Shell:

db.collection.aggregate([ 
 {
    $sort:
 {
      name: 1,
      age: -1
    }
  }
])

In this example, the documents in the aggregation pipeline will be sorted first by the "name" field in ascending order and then by the "age" field in descending order.


You can also use the $sort operator with other aggregation stages in a pipeline to control the order of operations. 

For example, you might want to sort the documents after a $match stage to filter the data and then apply further transformations.


It's important to note that the $sort operator can be resource-intensive, especially when sorting large result sets or on fields with high cardinality. 

MongoDB provides indexes to improve the efficiency of sorting operations.

 You can create indexes on the fields used for sorting to optimize the performance of the $sort stage.


The $sort operator in the MongoDB Shell allows you to order the documents in an aggregation pipeline based on specified criteria. 

It is a useful tool for organizing and presenting data in a desired order during the aggregation process.

Example: